Short circuiter



MM 23 192a.

E. P. LARSH SHORT CIRCUITER Filed Feb. 15, 1924 Patented Man 23, 1926. I

v UNITED STATES PATENT want I FF'i Q E a nvnanrr r. Luisa, or Darren,onro.

snofar cmcurrnn;

Application filed February 15, 1924. Serial No. 898,020.

I motor from a repulsion starting condition to equalize the shortcircuiting movement of to an induction running condition and vice versain accordance with variation of speed.

The, present construction embodies in a single structure theadvantageous features of both the governor weight and garter spring typeof short circuiting (lGVlCQS. ne of the purposes of the construction isan annular series of independent radially movable contact members toeffect the simultaneous engagement of all commutator bars. One of theobjectionable features of the garter spring type of short circuiter orone wherein the contact members oper ate against the yielding resistanceof a flexible retaining and retracting element is the tendency for thecontact members to move ununiformly. As the speed of rotationapproaches. the; critical point at which the short circuiting'devicesare to operate, the

tendency is to expand eccentrically or un-,

uniformly against the resistance of the flexible retainer. Thepontactmembers of such short 'circuiters of" the garter spring type beingloosely mounted in an annular series,

' some of the members may be held more loosely than others, due tovariation of the frictional contact or pressure laterally betweensucceeding, elements of the series. 'The tendency is for such looselyheld con;

tact elements tomove' outward into engagement with the commutator. barsin advance of the remaining contacts of the series. lVhile the contactsmay expand initially at one point, the eccentricity is of course onlymomentary, and immediately afterward the remaining contacts will expand.Thus while the defect is objectionable, it is not vital. However, tomeet certain conditions of use wherein precision and accuracy ofoperation is essential, and to conform to exacting trade requirements,and commercial efficiency tests, it is quite desirable that the movementof the contact elements be equalized, andany loosely held .elements beof contact members against the yielding resistance of which the membersare radially movableinto engagement with the commutator bars, undercentrifugal influence. The particular feature in the present instanceconsists in inter osing between the annular series of independentradially movable contact elements and the circumferential contractileretaining band an in flexible movable collar or equalizer, against whichthe contact members exert pressure in their outward or operativemovement, and which in turn transmits the pressure against the yieldinresistance of the circumferential contractile band.

The object of the invention is to simpli-i fy the structure as well asthe means and mode of operation of such circuit changing devices,whereby they .will not only be cheapened in construction, but will bemore efficient in use, automatic in operation, uniform vin .action,automatically controlled and unlikely to et out of repair.

A further ob ect of the invention is to provide such .centrifugallycontrolled short circuiting means which will ly to variations of speedabove and below a predetermined rate of rotation.

A.fu-rther and primary object of the invention is to provide a shortcircuiting or current changing device in which the movement of theoperating elements will be equalized, while employing a. flexible garterspring, or circumferential band, as there taining or retracting element.

respond promptjoints or indirect movements, but in which the currentcontrolling devices are directly operated by centrifugal tendency.

With the above primary and other incidental objects in view as will morefully appear in the specification, the invention consists of thefeatures of construction, the parts and combinations thereof, and themode of operation or their equivalents as hereinafter described and setforth in the claims.

In the accompanyin drawings, wherein is shown the preferre butobviously, not necessarily the only form of embodiment of the invention,Fig. 1 is a longitudinal sectional View of a motor commutator, to whichthe present form of short circuiting device has been applied. Fig. 2 isan end view thereof, with various parts broken away to expose underlyingportions. Figs. 3 and 4 are sectional views similar to Fig. 1,illustrating modifications.

Like parts are indicated by similar characters of reference upon theseveral views.

The structure of the electric motor per se, forms no part of the presentinvention, which pertains wholly to the short circuiting means for thecommutator bars, by which the motor is caused to operate alternately asa repulsion motor and an induction motor.

An alternating current, repulsion-induction motor of the single phasetype to whichthe present invention is particularly adapted is one whichas the name indicates, starts asa. repulsion motor and as the speedapproaches its normal or maximum rate of rotation automatically changesits character, and runs as an induction motor. Briefly described, itconsists of a field or stator of laminated toothed construction having asingle winding thereon connected to the sup-.

ply circuit and a progressively wound armature or rotor with acommutator engaged by brushes during the starting or repulsion periodtogether with speed controlled devices for short circuiting the armaturewindings through the commutator after the armature has attained apredetermined speed, which speed controlled means in some instanceslifts the brushes from the commutator simultaneously with the shortcircuiting operation. There is no electrical connection between thestator and the rotor. The currents in the stator create an alternatingflux which reacts on the rotor and induces its rotation. This type ofmotor, therefore, starts as a simple repulsion motor withoutcompensating or auxiliary windings and operates as a repulsion motoruntil the rotor or armature approaches a synchronous speed or onecommensurate with the windings, whereupon the speed controlleddevicesoperate to automatically short circuit the armature winding through thecommutator. Thus the motor is automatically trans:

formed from a repulsion type into an induction motor having what isessentially a squirrel cage rotor.. It is the improvement of the speedoperated governing or short circuiting device which forms the subjectmatter of the present invention. I

mature or its equivalent affords, themost' efficient motor when running.

. A repulsion-induction type of motor combines these most desirablequalities .in a single machine. As it possesses such high startingtorque characteristics it is well adapted for operating machinery whichstarts under full load, as pumps, air compressors, grindmg mills, andanalogous installatlons. Re-

quiring no starter, they are adapted for automatic control or distantoperation. They start quickly and operate quietly and smoothly; I a "Theabove is offered merely to facilitate a thoro understanding of thepurpose of the invention, and with no intent nor desire that it shall inany way be construed as limiting or restricting the application or scopeof the invention.

Inasmuch as the construction-of the motor per se forms no part of thisinvention, it has not been illustrated. It is to be understood, however,that the short circuiting means forming the subject matter hereof isapplicable "to various styles of motors of the character heretoforeindicated. Referring to the drawings, 1 is the armature shaft, on whichis carried the usual com-' mutator comprising the core 2 about theperiphery of which are located a continuous succession of commutatorbars 3, insulated from the core 2 and from each other by interveningbodies of insulating material.

In the present instance, the commutator bar is not an essential feature.

In the preferred embodiment of the invention as illustrated in thedrawing, there is employed a disc 6 secured to the armature shaft 1,adjacent to, but in spaced relation with the face of the commutator.Located intermediate the disc 6 and the lateral face of the commutatoris an annular series of independent contact members 7 These contactmembers are slightly sector or wedge shape, and are assembled side byside in an.

annular series, in which each contact member is radially disposed inrelation with the axis of rotation. Furthermore in such series, eachindependent contact member is laterally restrained and supported by thesucceeding contact members of the series and guided thereby in itsradial movement... As shown in Fig. 1, each of the contact clined ortapered exterior of the annular series of contact members, is an elasticflex ible retaining and retracting band 10. This band 10 preferablycomprises a helical spring, the ends of which are interconnected to forma continuous circular contractile member.

Upon rotation of the commutator and the series of contact members,centrifugal influence causes the contact member 7 to move outwardly in aradial direction against the yielding resistance of the circumferentialcontractile band 10. The contractile band 10 not only yieldingly resiststhe outward movement of the contact members 7, but dueto the inclinationof the exterior margins upon which the contractile or retract in ressureis a lied a ca min action is exertedby which the contac '?members arepressed inwardly toward the commutator, whereby as they move outwardlythey have a wiping or sliding engagement upon the ends of the commutatorbars. I,

As before mentioned, if the yielding resistance or spring tension of thecontractile" band 10 is applied directly to the" individual contactmember 7, some of the individual contact members which may be looselyheld between their neighboring members will res 0nd more quickly to thecentrifugal influence and will move outward against the flexibleyielding band, in advance of the main body of contact members. Suchpartial operation is. prevented in the present instance by interposingbetween the series of contact members and the contractile band 10, aninflexible tapered or inclfned collar 11, against-the innercircumference of which the tapered margins of the contact members exertoutward camming pressure and against the outer tapered circumference ofwhich the contractile band 10 exerts its retra'ctive pressure. The.

outer periphery of this tapered collar 11, extends in diagonal orangular relation with the plane of the disc 6. The contractile band10.is seated within the tapered groove or recess formed by the divergentrelation of the disc 6, and the interposed inflexible collar 11, Thecontractile or camming action of the circumferential band or spring '10tends to press the tapered collar 11 axially inward toward thecommutator, and against the tapered outer margins of the contactmembers. The contact members are thus subjected to pressure in twodirections. That is, inwardly in a radial direction toward the center ofrotation, and laterally in an axial direction toward the commutafl torface. The outward camming pressure of the inclined ends of the contactmembers upon the. interior surface of the tapered collar 11 tends to camsuch collar axially away from the commutator and toward the disc 6. Itis 'to' be noted that the collar is so proportioned and is of such widththat when urged inwardly by the contraction of the external band orspring 10, it occupies a spaced relation with the disc 6'. Thisclearance intermediate the tapered collar 11, and disc 6 permits itslateral movement as the contact members 7 move outwardly.

This. lateral shifting movement of the tapered collar 11, under outwardpressure of the contact members exerts an outward camming action uponthe contractile circumferential spring 10, expanding the spring againstthe yielding resistance of which the tapered collar 11 moves laterallyunder the outward radial pressure of the contact members due tocentrifugal influence. The operated relation of the parts is shown bydotted lines in Fig. 1. The tapered collar 11 serves to restrain anyloosely held contact members until the entire body of members issubjected to suflicient contrifugal influence to cause their movement inunison. Likewise if the spring 10 is of unequal resistance throughoutits extent possessing a tendency to yield more easily at one point thanat another, such condition is'corrected' by the interposed taperedcollar 11. To the contrary, the interposed tapered collar serves toconcentrate the entire resistance of the contractile band l0,upon anyloosely held slug or slugs, which might tend toward radial movement inadvance of the others. It is obvious that before any contact member orgroup of contact members can move radially in advance of the main b dy,of such members, Such member or members must force the tapered collar11 laterally against the retractive tension of the entire circular band10. Without such interposed inflexible tapered collar 11, there is atendency for the contact members to flex the retaining band locally oratone point only to accommodate such uneven expancontact members.

sion or advance movement of individual Such irregular or individualaction of the 'contact members is prevented by the interposed collar 11.

In order that the contact members may rotate in unison with thecommutator the disc 6 is preferably though not necessarily provided withinwardly projecting ears or lugs 12, at spaced intervals, which projectbetween succeeding contact members of the annular series separating theseries into groups and affording a driving connection which furthertends to guide the contact members in 'their radial movement.

In Figs. 3 and fl there is shown a modification, where in lieu of theannular tapered collar 11, previously described, there is employed-anaxially movable disc 13, having a tapered or inclined flange 14,projecting in divergent spaced relation with the disc 6. The contractileband or retaining member 10 is seated in the divergent groove or recessintermediate the inclined flange 14 and the disc 6, and by itscontraction tends to urge the disc 13 inwardly toward the commutatorface, The contact nem hers 7 are located intermediate the movable disc13, and the face of the commutator. These contact members 7 in theiroutward or radial movement, bear upon the inner inclined face of theflange 14, and exert an outward camming movement upon the disc 13,tending to move the disc axially away from the commutator, and in turnexert a camming influence upon the contractile band 10 expanding suchband against its yielding resistance as the disc 13 approaches the disc6. The function, operation and result of this construction issubstantially identical with that shown in Fig. 1 and previouslydescribed. Fig. 4

illustrates the parts mounted in a unitary structure, applicable to andremovable from the armature shaft without disassembly. The stationarydisc 6 and movable disc 13 are carried upon the laterally projectingcentral sleeve or hub 15 of a third disc adjacent to the face of thecommutator,

the contact members 7' being interposed between the disc 13 and the disc16. By

such construction the short circuiting unit may be assembled independentof the motor and subsequently applied thereto, or removed therefrom atwill, as a single integral structure.

In order that there may be driving engagement between the rotating partsand the contact members, the disc 16 may be radially beaded vorgroovedas may be de sired, or such radial lineal configuration may be formed inthe disc-13 to guide the contact members in their radial movement andinsure their rotation in unison with the commutator. I

From the above description it will be apparent that there is thusprovided a device of the character described possessing the particularfeatures of advantage before enumerated as desirable, but which obvi--ously is susceptible of modification in its forms, proportions, detailconstruction and arrangement of parts without departing from theprinciple involved or sacrificing any of its advantages.

While in order to comply with the'statute the invention has beendescribed in language more or less s eclfic as to struc--,

tural eatures, it is ,to understood that the invention is not limited tothe specific tators, an annular series of weights disposed--concentrically and radially in relation with the armature shaft, andmovable radially in relation thereto under centrifugal influence,

a flexible contractile band ciroum'ferentially surrounding the series ofweights against the tension of which the weights move 'radially undercentrifugal influence to effect the short circuiting of the commutator,and a yieldingly mounted inflexible band interposed between the weightsand spring restraining the unequal distension of the annular seriesof-weights.

2. In a short circuiter for motors, an annular expansible andcontractible series of centrifugally actuated weights an annular;

yielding tension spring against the resistance of which the weights moveradially under centrifugal influence to effect the short cir c-uiting ofthe motor armature, and an equalizing element interposed between theannular spring and the weights restraining the unequal distension of theannular series of weights.

3. Ina short circuiter for electric motors, an annular expansible andcontractible series of centrifugally actuated weights, an annularcontractile band circumferentially surrounding the weights against theresistance of which the weights are radially movable under influenceof'centrifugal influence, to effect the short circuiting of the motorarmature, and equalizing means additional to the circumferential bandfor yieldingly restraining .ununiform movement of the weights. i

4. In a short circuiter for electric motors, an annular series ofcentrifugally actuated weights, radially movable under influenceofcentrifugal influence, to effect the short oircuiting of the motorarmature, said series of weights being peripherally beveled, and

an inflexible tapered collar circumferentially surrounding the weightsand engaging with the beveled (peripheral face thereof, and

tending to yiel ngly restrain ununiform radial movement thereof, saidcollar being axially movable under the camming influence of the weights,and an expansible and contractible tension. element resisting thelateral movement of the collar and expanded by the .Wedging action ofthe tapered collar under expanding influence of the weights.

5. In a short circuiter for motors, an annular series of centrifugallyactuated weights, an axially movable abutment member engaged by theweights upon radial movement thereof-and restraining unequal movement ofsaid weights, said abutment member having an external tapered cam face,and a yielding tension member engaging the external tapered face of theabutment member to resist the axial movement thereof.-

"6. In a short circuiter. for motor commutators, an annular seriesof'centrifugally actated weights, said weights being beveled to presentan exterior inclined face divergent to the axis of rotation, an elasticcontractile u'ated weights, an annular contractile band against thetension of which the weights are radially movable to effect the shortcircuiting of the motor commutator, and an axially movable taperedcollar engaged by the weights upon radial movement tending to resistununiform expansion of the series of weights, said tapered collar beingexterio-rly engaged by the contractile band and laterally displaced bythe combined camming action of the weights during their radial movementagainst the tension of the contractile band.

In testimony whereof, I have hereunto set my hand this 28th day ofJanuary, A. D. 1924.

EVERETT P. LARSH.

